Inside the Cage Mushishi : Season 1 Episode 14

While resting in a bamboo forest, Ginko is approached by an odd man named Kisuke, who tells Ginko that he has been lost in the forest for 3 years. Ginko seems to have also become lost, and decides to go off and figure something out about the forest. After managing to get out of the forest, Ginko figures out that it's the work of a "Magaridake".